Allow PHP8

0.2.1

allow php 8

0.2.0

• Update dependency slepic/php-template to v0.2.
• Changed return type of TemplateDataProviderInterface::getTabData() and TemplateDataProviderInterface::getPanelData() to array.
• Changed travis setup to only run tests in oldest and newest php versions supported by this package (that is 5.6 and 7.3).

0.1.0

TemplatedBarPanel class
TemplateDataProviderInterface